The exemplary embodiments relate to a multi-projection display and a projector to use on the multi-projection display.
In the related art, there are multi-projection displays arranged with a plurality of projection optical units (assumed projectors) horizontally and vertically so that a large-area image can be displayed by projecting images from these projectors through tiling. Here, tiling projection means a projection scheme to display a large on-screen image by allocating, in a tiling form, the regions of projection from a plurality of projectors over the screen.
The multi-projection displays of the related art are capable of displaying an image higher in definition and brightness than those of the usual projectors. They are expected to broadly spread in the future, in the business field of movie theaters, art galleries, museums, seminar halls, assembly hall, minitheaters, public institutions and enterprises, as well as in the home-use fields of amusement and home theaters, or the like.
With the related art multi-projection displays, there is a general practice to partly overlap, over the screen, the projection images from adjacent ones of projectors. In partly overlapping the images projected from adjacent projectors over the screen in this manner, light intensity is higher at an overlap than at the other regions, raising a problem of conspicuous boundaries.
Particularly, with a projector using liquid-crystal light valves, the liquid-crystal light valve even for black (data value=0) in color is passed by a somewhat amount of light. Thus, there is a problem of so-called “black float”, i.e. light intensity is higher at an overlap of projection images from a plurality of projectors than at the regions free of overlaps.
FIG. 18 is a schematic explaining such “black float”. FIG. 18 shows a case in which tiling projection is carried out by four projectors, the light intensity of black being higher at an overlap 10 than at the other overlap-free regions. There are various proposals to solve problems associated with light intensity at overlap including an example described in JP-A-2001-268476.
JP-A-2001-268476 discloses an arrangement of a shade plate, etc. on the optical axis between the projector and the screen, to thereby adjust the light intensity at an overlap, making the light intensity at the overlap equivalent to that of other regions.
Meanwhile, some technologies cited in JP-A-2001-268476 describe that, by adopting shadow plates, light intensity at an overlap is made equivalent to those of other regions. For example, in JP-A-6-169444 cited in JP-A-2001-268476, there is a disclosure that the light intensity at the overlap is made equivalent to those of the other regions by providing a shadow plate on a lens unit having a projection lens.